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[Thermo] Convert Shomate coefficients when creating objects
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Do conversion to nondimensional units once when creating the ShomatePoly object,
instead of every time that properties are calculated.
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@speth
speth committed Jul 17, 2015
1 parent 761f54f commit b7a5aff
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Showing 2 changed files with 52 additions and 53 deletions.
78 changes: 25 additions & 53 deletions include/cantera/thermo/ShomatePoly.h
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Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,11 @@ class ShomatePoly : public SpeciesThermoInterpType
*/
ShomatePoly(double tlow, double thigh, double pref, const double* coeffs) :
SpeciesThermoInterpType(tlow, thigh, pref),
m_coeff(coeffs, coeffs + 7)
m_coeff(7)
{
for (size_t i = 0; i < 7; i++) {
m_coeff[i] = coeffs[i] * 1000 / GasConstant;
}
}

virtual SpeciesThermoInterpType*
Expand All @@ -85,7 +88,7 @@ class ShomatePoly : public SpeciesThermoInterpType
return SHOMATE;
}

virtual size_t temperaturePolySize() const { return 7; }
virtual size_t temperaturePolySize() const { return 6; }

virtual void updateTemperaturePoly(double T, double* T_poly) const {
doublereal tt = 1.e-3*T;
Expand All @@ -94,8 +97,7 @@ class ShomatePoly : public SpeciesThermoInterpType
T_poly[2] = T_poly[1] * tt;
T_poly[3] = 1.0/T_poly[1];
T_poly[4] = std::log(tt);
T_poly[5] = 1.0/GasConstant;
T_poly[6] = 1.0/(GasConstant * T);
T_poly[5] = 1.0/tt;
}

//! Update the properties for this species, given a temperature polynomial
Expand All @@ -105,14 +107,13 @@ class ShomatePoly : public SpeciesThermoInterpType
* pointers to arrays where the computed property values should be
* written. This method updates only one value in each array.
*
* - `tt` is T/1000.
* - `m_t[0] = tt`
* - `m_t[1] = tt*tt`
* - `m_t[2] = m_t[1]*tt`
* - `m_t[3] = 1.0/m_t[1]`
* - `m_t[4] = log(tt)`
* - `m_t[5] = 1.0/GasConstant`
* - `m_t[6] = 1.0/(GasConstant * T)`
* - `t` is T/1000.
* - `t[0] = t`
* - `t[1] = t*t`
* - `t[2] = t[1]*t`
* - `t[3] = 1.0/t[1]`
* - `t[4] = log(t)`
* - `t[5] = 1.0/t;
*
* @param tt Vector of temperature polynomials
* @param cp_R Vector of Dimensionless heat capacities. (length m_kk).
Expand All @@ -128,32 +129,18 @@ class ShomatePoly : public SpeciesThermoInterpType
doublereal Ct2 = m_coeff[2]*tt[1];
doublereal Dt3 = m_coeff[3]*tt[2];
doublereal Etm2 = m_coeff[4]*tt[3];
doublereal F = m_coeff[5];
doublereal Ftm1 = m_coeff[5]*tt[5];
doublereal G = m_coeff[6];

doublereal cp, h, s;
cp = A + Bt + Ct2 + Dt3 + Etm2;
h = tt[0]*(A + 0.5*Bt + 1.0/3.0*Ct2 + 0.25*Dt3 - Etm2) + F;
s = A*tt[4] + Bt + 0.5*Ct2 + 1.0/3.0*Dt3 - 0.5*Etm2 + G;

/*
* Shomate polynomials parameterizes assuming units of
* J/(gmol*K) for cp_r and s_R and kJ/(gmol) for h.
* However, Cantera assumes default MKS units of
* J/(kmol*K). This requires us to multiply cp and s
* by 1.e3 and h by 1.e6, before we then nondimensionalize
* the results by dividing by (GasConstant * T),
* where GasConstant has units of J/(kmol * K).
*/
*cp_R = 1.e3 * cp * tt[5];
*h_RT = 1.e6 * h * tt[6];
*s_R = 1.e3 * s * tt[5];
*cp_R = A + Bt + Ct2 + Dt3 + Etm2;
*h_RT = A + 0.5*Bt + 1.0/3.0*Ct2 + 0.25*Dt3 - Etm2 + Ftm1;
*s_R = A*tt[4] + Bt + 0.5*Ct2 + 1.0/3.0*Dt3 - 0.5*Etm2 + G;
}

virtual void updatePropertiesTemp(const doublereal temp,
doublereal* cp_R, doublereal* h_RT,
doublereal* s_R) const {
double tPoly[7];
double tPoly[6];
updateTemperaturePoly(temp, tPoly);
updateProperties(tPoly, cp_R, h_RT, s_R);
}
Expand All @@ -168,7 +155,7 @@ class ShomatePoly : public SpeciesThermoInterpType
thigh = m_highT;
pref = m_Pref;
for (int i = 0; i < 7; i++) {
coeffs[i] = m_coeff[i];
coeffs[i] = m_coeff[i] * GasConstant / 1000;
}
}

Expand All @@ -178,36 +165,21 @@ class ShomatePoly : public SpeciesThermoInterpType
* parameters for the standard state.
*/
virtual void modifyParameters(doublereal* coeffs) {
if (m_coeff.size() != 7) {
throw CanteraError("modifyParameters",
"modifying something that hasn't been initialized");
for (size_t i = 0; i < 7; i++) {
m_coeff[i] = coeffs[i] * 1000 / GasConstant;
}
std::copy(coeffs, coeffs + 7, m_coeff.begin());
}

virtual doublereal reportHf298(doublereal* const h298 = 0) const {
double tPoly[7];
updateTemperaturePoly(298.15, tPoly);
doublereal A = m_coeff[0];
doublereal Bt = m_coeff[1]*tPoly[0];
doublereal Ct2 = m_coeff[2]*tPoly[1];
doublereal Dt3 = m_coeff[3]*tPoly[2];
doublereal Etm2 = m_coeff[4]*tPoly[3];
doublereal F = m_coeff[5];

doublereal h = tPoly[0]*(A + 0.5*Bt + 1.0/3.0*Ct2 + 0.25*Dt3 - Etm2) + F;

double hh = 1.e6 * h;
if (h298) {
*h298 = 1.e6 * h;
}
return hh;
double cp_R, h_RT, s_R;
updatePropertiesTemp(298.15, &cp_R, &h_RT, &s_R);
return h_RT * GasConstant * 298.15;
}

virtual void modifyOneHf298(const size_t k, const doublereal Hf298New) {
doublereal hnow = reportHf298();
doublereal delH = Hf298New - hnow;
m_coeff[5] += delH / 1.0E6;
m_coeff[5] += delH / (1e3 * GasConstant);
}

protected:
Expand Down
27 changes: 27 additions & 0 deletions test/thermo/thermoParameterizations.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,3 +103,30 @@ TEST_F(SpeciesThermoInterpTypeTest, install_shomate)
EXPECT_DOUBLE_EQ(p2.entropy_mass(), p.entropy_mass());
EXPECT_DOUBLE_EQ(p2.cp_mass(), p.cp_mass());
}

TEST(Shomate, modifyParameters)
{
ShomatePoly2 S1(200, 6000, 101325, co2_shomate_coeffs);
ShomatePoly2 S2(200, 6000, 101325, co_shomate_coeffs);

S2.modifyParameters((double*) co2_shomate_coeffs);
double cp1, cp2, h1, h2, s1, s2;
S1.updatePropertiesTemp(500, &cp1, &h1, &s1);
S2.updatePropertiesTemp(500, &cp2, &h2, &s2);
EXPECT_DOUBLE_EQ(cp1, cp2);
EXPECT_DOUBLE_EQ(h1, h2);
EXPECT_DOUBLE_EQ(s1, s2);
}

TEST(Shomate, modifyOneHf298)
{
ShomatePoly2 S(200, 6000, 101325, co2_shomate_coeffs);

EXPECT_NEAR(-393.5224e6, S.reportHf298(), 1e4);
double Htest = -400e6;
S.modifyOneHf298(npos, Htest);
double cp, h, s;
S.updatePropertiesTemp(298.15, &cp, &h, &s);
EXPECT_DOUBLE_EQ(Htest, h * 298.15 * GasConstant);
EXPECT_DOUBLE_EQ(Htest, S.reportHf298());
}

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